A space reactor control method based on double protection of control loop and reflecting layer

Abstract

The application relates to a space reactor control method based on double protection of a control ring and a reflection layer, and the method comprises the following steps: constructing a space reactor, and completing effective safety control of the space reactor through cooperation between a reactor core fuel area, a control ring, a radial reflection layer, an axial reflection layer, a sensor and a reaction instrument in the space reactor; safety shutdown of the reactor can be realized through two sets of adjustment schemes of the control ring and the radial reflection layer, and a double protection mechanism is provided. Through design of control values of the control ring and the radial reflection layer respectively, the control value of the radial reflection layer is greater than the control value of the control ring, cooperative control of coarse adjustment of reactivity by the radial reflection layer and fine adjustment of reactivity by the control ring can be realized, and the space reactor can realize safe and efficient and flexible control.

Description

Technical Field

[0001] This application relates to the field of reactor safety technology, and in particular to a space reactor control method based on dual protection of a control loop and a reflector layer. Background Technology

[0002] As humanity delves deeper into outer space, the demands for power sources are increasing. Space nuclear reactors offer significant advantages and promising applications in areas such as powering Earth-orbiting satellites, deep-space probes, and lunar and Martian bases. Compared to isotope-based power sources, space reactors are independent of sunlight, have good environmental adaptability, a significantly lower power-to-weight ratio with increasing power, and are highly maneuverable. Furthermore, when combined with electric thrusters, they form nuclear electric propulsion systems with high specific impulse and substantial thrust. Based on their core cooling methods, space nuclear reactors are mainly classified into three types: liquid metal-cooled reactors, gas-cooled reactors, and heat pipe-cooled reactors. Currently, small-scale space nuclear reactors, such as the Kilopower heat pipe-cooled reactor, have completed relevant tests, demonstrating substantial progress in their application in aerospace and marine exploration. Domestic research on space reactors in China is currently focusing on core physics and thermal design, material selection, and the research and testing of their inherent safety characteristics.

[0003] Developing a practical, effective, safe, and reliable safety control scheme for space reactors is an important research topic for space reactor safety and a key to its engineering application. Among the existing reactor control schemes, there are mainly the following methods: (1) arranging control rods containing strong neutron absorbers such as B4C in the reactor core to control the reactivity of the core; (2) using a solution containing boric acid to inject coolant to control the reactivity of the core; (3) arranging combustible poisons in the reactor core to control reactivity; (4) using a reflector layer to change the neutron leakage rate of the reactor core to control reactivity; (5) arranging a control drum containing strong neutron absorbers such as B4C outside the reactor core to control reactivity.

[0004] However, because space nuclear reactor systems need to be miniaturized and lightweight as much as possible to meet the size and mass constraints of space missions, traditional methods such as in-core control rods can introduce significant core neutron field disturbances in miniaturized space reactors. Furthermore, when using external methods such as reflectors and control drums, it is necessary to consider control safety under conditions of related system failures. In addition, current space reactors are typically designed to carry highly enriched nuclear materials. 235 The reactor uses nuclear fuel and is designed to operate in a fast reactor mode. To ensure the long-term stable and safe operation and energy supply of the reactor in extreme space environments such as weightlessness or microgravity, cosmic ray radiation, and low temperature, while also taking into account miniaturization and lightweighting, and achieving goals such as efficient and safe control and system reliability, it is necessary to design relevant safe and effective space reactor control schemes. SUMMARY

[0005] Therefore, it is necessary to provide a space reactor control method based on double protection of control ring and reflector layer for the above technical problems.

[0006] A space reactor control method based on double protection of control ring and reflector layer, comprising the following steps:

[0007] constructing a space reactor; the space reactor comprises a core fuel region, an axial reflector layer, a radial reflector layer, a control ring, a sensor and a reactivity instrument; the control ring is arranged between the core fuel region and the radial reflector layer; the radial reflector layer is arranged radially outside the control ring; the reactivity instrument is arranged at the periphery of the radial reflector layer for real-time measurement of the reactivity of the core of the space reactor; the sensor is arranged inside and outside the radial reflector layer and the axial reflector layer for measurement of temperature and pressure; wherein the reactivity of the core is negatively correlated with the area of the core fuel region opposite to the control ring and positively correlated with the area of the core fuel region opposite to the radial reflector layer;

[0008] the control values of the control ring and the radial reflector layer are respectively designed so that the control value of the radial reflector layer is greater than the control value of the control ring; the control value represents the corresponding reactivity change value when a unit axial height is moved; the ratio of the control value of the radial reflector layer to the control value of the control ring is (2-5):1;

[0009] obtaining the currently measured reactivity, calculating the effective multiplication factor corresponding to the reactivity value, and calculating the absolute value of the difference between the preset adjusted core effective multiplication factor and the current core effective multiplication factor when the temperature measured by the sensor does not exceed the preset temperature and the pressure does not exceed the preset pressure;

[0010] if the absolute value is greater than the preset value, the axial height of the radial reflector layer is adjusted according to the control value of the radial reflector layer, and if the absolute value is not greater than the preset value, the axial height of the control ring is adjusted according to the control value of the control ring.

[0011] In the above space reactor control method based on double protection of control ring and reflector layer, the space reactor is constructed, and the effective safety control of the space reactor is completed through the cooperation between the core fuel region, the control ring, the radial reflector layer, the axial reflector layer, the sensor and the reactivity instrument therein. The safety shutdown of the reactor can be realized through the two sets of adjustment schemes of the control ring and the radial reflector layer, which has a double protection mechanism. By respectively designing the control values of the control ring and the radial reflector layer, the control value of the radial reflector layer is greater than the control value of the control ring, so that the cooperative control of the coarse adjustment of the reactivity by the radial reflector layer and the fine adjustment of the reactivity by the control ring can be realized, and the space reactor can be safely and efficiently and flexibly controlled. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 This is a schematic flowchart of a space reactor control method based on dual protection of a control loop and a reflector layer in one embodiment;

[0013] Figure 2 This is a structural diagram of a radial arrangement scheme for a space reactor control system based on dual protection of a control loop and a reflector layer in one embodiment;

[0014] Figure 3 This is a structural diagram of the axial arrangement of a space reactor control system based on dual protection of the control loop and the reflector layer in one embodiment;

[0015] Figure 4 This is a schematic diagram of the radial arrangement of a space reactor control system based on dual protection of the control loop and the reflector layer, carried out on a 10kW electric power heat pipe stack Kilopower in another embodiment.

[0016] Figure 5 In one embodiment, a control scheme based on a dual protection system of control loops and reflectors was developed on a 10 kW electric power heat pipe reactor, Kilopower. The radial reflectors are all axially aligned with the reactor core. Under a sand fall accident, the axial height of the control loops relative to the reactor core is varied. eff The impact;

[0017] Figure 6 In one embodiment, a control scheme based on a dual-protection system of control loop and reflector layer for a space reactor was developed on a 10kW electric power heat pipe reactor, Kilopower. The control scheme was implemented with the radial reflector layer fully extracted axially towards the reactor core. Under a sand fall accident, the axial height of the control loop was adjusted relative to the reactor core k. eff The impact;

[0018] Figure 7 In one embodiment, a control scheme based on a dual protection mechanism of control loops and reflectors was developed on a 10 kW electric power heat pipe reactor, Kilopower. The radial reflectors are all axially aligned with the reactor core. The axial height of the control loops varies depending on the reactor core height under different conditions, such as during a launch accident or a water ingress accident. eff The impact;

[0019] Figure 8 In a specific embodiment of the present invention, a control scheme based on a dual protection mechanism of control loop and reflector layer for a space reactor control system developed on a 10kW electric power heat pipe reactor Kilopower is described. The control scheme involves the radial reflector layer being completely extracted axially towards the reactor core. Under different axial heights of the control loop and the reactor core under launch accidents and water ingress accidents, the control scheme is applied to the reactor core. eff The impact.

[0020] Figure 9 The control scheme of the control system of the space reactor based on the double protection of the control ring and the reflector layer, which is carried out in the specific embodiment of the present application on the 10kW electric power heat pipe reactor Kilopower, has the transient influence of the normalized neutron density in the core with time under the condition of introducing different positive reactivity values into the core.

[0021] Figure 10 The control scheme of the control system of the space reactor based on the double protection of the control ring and the reflector layer, which is carried out in the specific embodiment of the present application on the 10kW electric power heat pipe reactor Kilopower, has the transient influence of the normalized neutron density in the core with time under the condition of introducing different negative reactivity values into the core. DETAILED DESCRIPTION

[0022] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0023] In one embodiment, as shown in Figure 1 a space reactor control method based on the double protection of the control ring and the reflector layer is provided, comprising the following steps:

[0024] Step 102, constructing a space reactor.

[0025] The space reactor comprises a core fuel region, an axial reflector, a radial reflector, a control ring, a sensor and a reactivity instrument.

[0026] The control ring is arranged between the core fuel region and the radial reflector;

[0027] The radial reflector is arranged radially outside the control ring, and the axial reflector is arranged and fixed at the axial two ends of the core fuel region, respectively;

[0028] The reactivity instrument is arranged at the periphery of the radial reflector for real-time measurement of the reactivity p of the core of the space reactor;

[0029] The sensor is arranged inside and outside the radial reflector and the axial reflector for measuring temperature and pressure;

[0030] The reactivity of the reactor core is negatively related to the area of the control ring directly opposite the fuel area of the reactor core and positively related to the area of the radial reflector directly opposite the fuel area of the reactor core, that is, when the radial reflector is axially moved to a position directly opposite the fuel area of the reactor core, the neutrons can be multiplied and reflected back to the fuel area of the reactor core, the nuclear fission reaction rate in the reactor core is increased, and thus the reactivity of the reactor core is increased; when the radial reflector is partially or entirely axially moved to a position deviating from the position directly opposite the fuel area of the reactor core, the neutron multiplication reaction process is reduced, the nuclear fission reaction rate in the reactor core is reduced, and thus the reactivity of the reactor core is reduced.

[0031] In step 104, the control values of the control ring and the radial reflector are respectively designed, so that the control value of the radial reflector is greater than the control value of the control ring.

[0032] The control value represents the change value of the reactivity p corresponding to the movement of a unit axial height. The ratio of the control value of the radial reflector to the control value of the control ring is (2-5):1.

[0033] In the control value design, the control value (pcm / cm) of the control ring is designed to be smaller than the control value (pcm / cm) of the radial reflector, that is, the change of the reactivity caused by the movement of the radial reflector is greater than that of the control ring when the axial height is the same. The real-time reactivity monitoring is performed through the reactivity monitoring system, the fine adjustment of the reactivity is performed by the control ring, and the coarse adjustment of the reactivity is performed by the radial reflector.

[0034] In step 106, the current measured reactivity p is obtained. (n-1) In step 107, the effective multiplication factor corresponding to the reactivity value is calculated. When the temperature measured by the sensor does not exceed the preset temperature and the pressure does not exceed the preset pressure, the absolute value of the difference between the preset adjusted effective multiplication factor of the reactor core and the current effective multiplication factor of the reactor core is calculated.

[0035] The effective multiplication factor of the adjusted reactor core can be set to The effective multiplication factor of the adjusted reactor core can be set to

[0036] In step 108, if the absolute value is greater than the preset value, the axial height of the radial reflector is adjusted according to the control value of the radial reflector; if the absolute value is not greater than the preset value, the axial height of the control ring is adjusted according to the control value of the control ring.

[0037] When the temperature measured by the sensor does not exceed the preset temperature and the pressure does not exceed the preset pressure, it represents that the shutdown is not needed, and at this time, the preset value is generally set to ​​It can be understood that, by controlling the ring or the radial reflector alone, effective shutdown can be achieved, i.e., the effective multiplication factor keff of the reactor core is less than 1, for example, by moving the ring axially (at this time, the radial reflector is axially fully opposite to the fuel region of the reactor core), or by moving the radial reflector axially out of the position opposite to the fuel region of the reactor core (at this time, the ring is axially moved out of the position opposite to the fuel region of the reactor core).

[0038] The preset value can be 0.005, 0.01 or 0.05, and can be set according to actual needs. When the preset value is 0.05, there is:

[0039] If , the next adjustment of the ring is performed by driving the ring to move axially.

[0040] If , the next adjustment of the ring is performed by driving the ring to move axially.

[0041] The ring and the radial reflector each have a corresponding driving mechanism for adjusting the axial height. Thus, by measuring the reactivity in real time by the reactivity instrument, different instructions are sent to the corresponding driving mechanisms according to the above steps, so that the ring and the radial reflector are cooperatively controlled.

[0042] The above space reactor control method based on the double protection of the ring and the reflector includes: constructing a space reactor, and completing effective and safe control of the space reactor through the cooperation between the fuel region of the reactor core, the ring, the radial reflector, the axial reflector, the sensor and the reactivity instrument. Safe shutdown of the reactor can be achieved by the two sets of adjustment schemes of the ring and the radial reflector, and the double protection mechanism is provided. By respectively designing the control values of the ring and the radial reflector, the control value of the radial reflector is greater than that of the ring, so that the cooperative control of the radial reflector on the coarse adjustment of the reactivity and the ring on the fine adjustment of the reactivity is achieved, and flexible control of the space reactor is achieved.

[0043] In one embodiment, there is a real space gap between the ring, the fuel region of the reactor core and the radial reflector, for providing geometric space for thermal expansion and contraction of the corresponding components.

[0044] In one embodiment, the control values of the ring and the radial reflector are respectively designed, including:

[0045] The control value of the ring is designed, specifically including: adjusting the proportion of the neutron absorber in the ring, or the inner and outer radial dimensions of the ring; the higher the proportion of the neutron absorber, the greater the control value of the ring; the greater the geometric volume corresponding to the inner and outer radial dimensions, the greater the control value of the ring. ​​

[0046] The control value of designing a radial reflector layer specifically includes: adjusting the proportion of neutron multiplier material in the radial reflector layer, or the inner and outer radial dimensions of the radial reflector layer; among them, the higher the proportion of neutron multiplier material, the greater the control value of the radial reflector layer; the larger the geometric volume corresponding to the inner and outer radial dimensions, the greater the control value of the radial reflector layer.

[0047] The control loop is mainly composed of a neutron absorber and structural materials. Its control value can be designed by adjusting the proportion of the neutron absorber, such as the volume or mass percentage of B4C, and the inner and outer radial dimensions of the control loop. The control value (pcm / cm) is calculated by determining the change in reactivity resulting from moving different axial heights. When it is necessary to increase the control value of the control loop, this can be achieved by increasing the proportion of the neutron absorber, such as the volume or mass percentage of B4C, or by increasing the geometric volume of the control loop.

[0048] The radial and axial reflectors are mainly composed of neutron multiplier materials such as BeO and structural materials. The control value of the radial reflector can be designed by considering the volume or mass percentage of BeO, the inner and outer radial dimensions of the radial reflector, and the axial thickness of the axial reflector. For the radial reflector, the control value (pcm / cm) is calculated by altering its reactivity at different axial heights. When it is necessary to increase the control value of the radial reflector, the volume or mass percentage of BeO can be increased, or the geometric volume of the radial reflector can be increased. Furthermore, in the radial reflector design, if the entire radial reflector is moved away from the position directly opposite the fuel zone in the core, the core cannot achieve criticality (keff < 1).

[0049] In the control value design of the control loop and radial reflector, safe shutdown can be achieved by axially moving either the control loop or the radial reflector alone. That is, by axially moving the control loop alone (in which case the radial reflector is completely axially aligned with the core fuel zone), or by moving the radial reflector completely axially away from the position directly aligned with the core fuel zone (in which case the control loop is completely axially moved away from the position directly aligned with the core fuel zone), the effective core growth factor k can be achieved. eff <1.

[0050] In one embodiment, the radial reflective layer is divided into four sections according to four quadrants;

[0051] like If the absolute value is greater than the preset value, the axial height of the radial reflective layer is adjusted according to the control value of the radial reflective layer, including:

[0052] Will The range of values ​​greater than a preset value is divided into four preset ranges;

[0053] When the absolute value is located in the first interval, the axial height of the corresponding radial reflecting layer is adjusted in turn according to the order of the first quadrant to the fourth quadrant until the absolute value is not greater than the preset value; if the radial reflecting layers of the four quadrants all exceed the axial movement distance and still cannot realize the next adjustment, the axial movement of the control ring is driven again;

[0054] When the absolute value is located in the second interval, the axial height of the radial reflecting layers of the first quadrant and the third quadrant is adjusted first until the absolute value is not greater than the preset value or reaches the adjustment limit, if the adjustment limit is reached and the absolute value is still greater than the preset value, then the axial height of the radial reflecting layers of the second quadrant and the fourth quadrant is adjusted in turn until the absolute value is not greater than the preset value; if the radial reflecting layers of the four quadrants all exceed the axial movement distance and still cannot realize the next adjustment, the axial movement of the control ring is driven again;

[0055] When the absolute value is located in the third interval, the axial height of the radial reflecting layers of the first quadrant, the second quadrant and the third quadrant is adjusted first until the absolute value is not greater than the preset value or reaches the adjustment limit, if the adjustment limit is reached and the absolute value is still greater than the preset value, then the axial height of the radial reflecting layer of the fourth quadrant is adjusted until the absolute value is not greater than the preset value; if the radial reflecting layers of the four quadrants all exceed the axial movement distance and still cannot realize the next adjustment, the axial movement of the control ring is driven again;

[0056] When the absolute value is located in the fourth interval, the radial reflecting layers of the first quadrant, the second quadrant, the third quadrant and the fourth quadrant are simultaneously driven to move axially until the absolute value is not greater than the preset value; if the adjustment limit is reached and the absolute value is still greater than the preset value, then the axial movement of the control ring is driven again until the absolute value is not greater than the preset value.

[0057] Among them, the closeness of the four preset intervals to the preset value is improved in turn from the first interval to the fourth interval.

[0058] Taking the preset value 0.05 as an example: in the implementation of the above steps, when the radial reflecting layer driving mechanism receives the instruction to drive the axial movement of the radial reflecting layer,

[0059] if

[0060] then according to the order of the first quadrant to the fourth quadrant, first drive the radial reflector layer of the first quadrant to move axially, if the radial reflector layer of the first quadrant still cannot achieve the next adjustment after exceeding the distance of axial movement, drive the radial reflector layer of the second quadrant to move axially; if the radial reflector layer of the second quadrant still cannot achieve the next adjustment after exceeding the distance of axial movement, drive the radial reflector layer of the third quadrant to move axially; if the radial reflector layer of the third quadrant still cannot achieve the next adjustment after exceeding the distance of axial movement, drive the radial reflector layer of the fourth quadrant to move axially; if the radial reflector layers of the four quadrants still cannot achieve the next adjustment after exceeding the distance of axial movement, drive the control ring to move axially again.

[0061] if

[0062] then according to the order of the first quadrant to the fourth quadrant, first drive the radial reflector layer of the first quadrant, the third quadrant to move axially, if the radial reflector layer of the first quadrant, the third quadrant still cannot achieve the next adjustment after exceeding the distance of axial movement, drive the radial reflector layer of the second quadrant, the fourth quadrant to move axially; if the radial reflector layers of the four quadrants still cannot achieve the next adjustment after exceeding the distance of axial movement, drive the control ring to move axially again.

[0063] if

[0064] then according to the order of the first quadrant to the fourth quadrant, first drive the radial reflector layer of the first quadrant, the second quadrant, the third quadrant to move axially, if the radial reflector layer of the first quadrant, the second quadrant, the third quadrant still cannot achieve the next adjustment after exceeding the distance of axial movement, drive the radial reflector layer of the fourth quadrant to move axially; if the radial reflector layers of the four quadrants still cannot achieve the next adjustment after exceeding the distance of axial movement, drive the control ring to move axially again.

[0065] if

[0066] then drive the radial reflector layer of the first quadrant, the second quadrant, the third quadrant, the fourth quadrant to move axially at the same time, if the radial reflector layers of the four quadrants still cannot achieve the next adjustment after exceeding the distance of axial movement, drive the control ring to move axially again;

[0067] ​​​​​​​​​Thus, the reactivity is measured in real time by the reactivity instrument, and after sending different instructions to the corresponding driving mechanisms according to the above steps, the coordinated control of the four radial reflector layers is realized.

[0068] If the four quadrant radial reflector layers still cannot achieve the preset effective multiplication factor of the core after the adjustment, the axial movement of the driving control ring is driven.

[0069] In one embodiment, the corresponding effective multiplication factor is calculated according to the reactivity value, and the method is:

[0070]

[0071] Wherein, k eff represents the effective multiplication factor, and p represents the reactivity of the spatial reactor core.

[0072] In one embodiment, the core fuel area includes a startup neutron source, a fuel element, a heat conduction element, and a base material;

[0073] The heat conduction element is a liquid alkali metal heat pipe or a cooling loop pipe containing a cooling working medium; the cooling working medium is an inert gas or a liquid metal;

[0074] The thermoelectric conversion device is a thermoelectric generator or a Stirling engine;

[0075] The hot end of the heat conduction element is arranged around the fuel element, and the cold end is connected to the thermoelectric conversion device, which is used to carry out the heat released by the fuel element and convert it into electrical energy through the thermoelectric conversion device;

[0076] The heat conduction element is a liquid alkali metal heat pipe or a cooling loop pipe containing a cooling working medium; the cooling working medium is an inert gas (such as helium) or a liquid metal (such as Na or K or NaK);

[0077] The thermoelectric conversion device is a thermoelectric generator or a Stirling engine.

[0078] Wherein the startup neutron source (such as Am-Be source or 252 Cf, etc.) is used to start the reactor, the fuel element is ignited by the startup neutron source, and the fission reaction occurs to release fission energy, the hot end of the heat conduction element is arranged around the fuel element, the cold end of the heat conduction element is connected to the thermoelectric conversion device, which is used to carry out the energy released by the fission of the fuel element, and the energy utilization is realized through the thermoelectric conversion device, and the base material is mainly a structural material with good high-temperature resistance, radiation resistance, and mechanical properties, such as Mo or Mo-Re alloy, etc. Part of the converted electrical energy is used to drive the mechanical driving devices of the control ring and the radial reflector layer, and the axial height of the control ring or the radial reflector layer is adjusted according to the feedback of the reactivity instrument.

[0079] In one embodiment, when the temperature measured by the sensor exceeds a preset temperature, the pressure exceeds a preset pressure, and a portion of the electrical energy converted by the thermoelectric conversion device can drive the axial height adjustment device, the axial height of the radial reflector is adjusted so that the radial reflector is partially or completely offset from the core fuel area, or the axial height of the control ring is adjusted so that the control ring is partially or completely aligned with the core fuel area, in order to reduce reactivity.

[0080] In one embodiment, the sensor consists of a strain gauge and a data acquisition box;

[0081] The space reactor also includes: an emergency shutdown system and energy storage components;

[0082] The emergency shutdown system includes a power supply unit;

[0083] The energy storage component includes a connected thermocouple and an energy storage battery. The thermocouple can convert thermal energy into electrical energy and charge the energy storage battery, enabling the energy storage battery to serve as a backup power source. The energy storage battery can be a lithium battery or the like.

[0084] In one embodiment, when the temperature measured by the sensor exceeds a preset temperature, the pressure exceeds a preset pressure, and a portion of the electrical energy converted by the thermoelectric conversion device is insufficient to drive the axial height adjustment device, the energy storage battery is activated to provide power to adjust the axial height of the reflective layer to reduce reactivity.

[0085] In one embodiment, when the temperature measured by the sensor exceeds a preset temperature, the pressure exceeds a preset pressure, and a portion of the electrical energy converted by the thermoelectric conversion device is insufficient to drive the axial height adjustment device, and the energy storage battery loses power, the radial reflector layer is ejected to increase the neutron leakage rate of the core and ensure that the core does not experience a supercritical event.

[0086] The following beneficial effects can be achieved by using the present invention:

[0087] This invention first constructs a space reactor control system based on dual protection of the control loop and the reflector layer. The second step involves the coordinated operation of the core fuel zone, control loop, radial reflector layer, axial reflector layer, sensors and energy storage components, reactivity meter, and emergency shutdown system to achieve effective and safe control of the space reactor. The control loop and radial reflector layer, through two adjustment schemes, can both achieve safe reactor shutdown, providing a dual protection mechanism. In the emergency shutdown system, a portion of the electrical energy converted by thermoelectric conversion equipment or the backup power from the charging of energy storage batteries can drive the mechanical drive devices of the control loop and radial reflector layer, achieving effective control of the two dual protection mechanisms. Furthermore, in the event of the loss of these two power sources, the expansion effect of temperature and pressure can eject the radial reflector layers in all four quadrants directly opposite the core, increasing the neutron leakage rate of the core and ensuring that the core does not experience neutron leakage. effThe supercritical event >1 fully realizes the effective safety control of the space reactor.

[0088] This invention provides a safe and effective control scheme for future space reactor applications, which can fully protect the safety of the reactor system and the environment, while achieving the goals of miniaturization and lightweighting of space reactors, and improving the system's durability and economic practicality.

[0089] like Figure 2 The diagram shows a radial layout scheme for a space reactor control system based on dual protection of the control loop and the reflector layer.

[0090] like Figure 3 The diagram shows the axial arrangement of a space reactor control system based on dual protection of the control loop and the reflector layer.

[0091] like Figure 4 The diagram shown is a schematic representation of the radial arrangement of a space reactor control system based on dual protection of a control loop and a reflector layer, implemented in a specific embodiment of the present invention on a 10kW electric power heat pipe reactor, Kilopower. Kilopower is a kW-class electric power space reactor proposed in 2010, which uses blocky uranium-molybdenum alloy (U-Mo) as fuel. The U-Mo alloy contains... 235 With a U enrichment of 93%, the reflector layer is made of beryllium oxide (BeO) material, arranged radially and axially in the fuel zone of the core. The heat-conducting elements are heat pipes filled with liquid alkali metal Na, which remove core heat and transfer it to the Stirling generator for thermoelectric conversion to produce electricity. The remaining waste heat is carried away by heat pipes filled with water and discharged into space through aluminum radiating plates. In March 2018, Kilopower's ground-based experimental reactor KRUSTY completed nuclear operation testing. The core parameters of the 10kW electric power Kilopower heat pipe reactor are shown in Table 1. The design parameters of the space reactor control system based on dual protection of control loop and reflector layer on the 10kW electric power heat pipe reactor Kilopower are shown in Table 2. The control loop material is B4C, which is a ring of neutron absorbing material mixed with boron and carbon. It is used to adjust the neutron flux in the reactor and is arranged between the reactor core and the radial reflector layer. Since the B4C control loop has a high neutron absorption cross section, it is connected to a mechanical drive device that can adjust the axial height of the control loop. By combining the feedback of the reactivity meter, it can move in different axes.

[0092] The space gaps of 1.5mm are reserved between the fuel region and the B4C control ring, and between the B4C control ring and the radial reflector, so as to prevent the B4C control ring from being stuck when being pulled out. The radial reflector and the axial reflector are composed of BeO containing neutron multiplication material. The axial reflector is fixed at the axial ends of the fuel region, and the radial reflector is divided into four parts according to four quadrants, and each part is connected with a mechanical driving device capable of adjusting the axial height. The fission neutrons generated in the core can have neutron multiplication reaction with the Be material in the axial reflector and the radial reflector, and the reaction process is as follows:

[0093]

[0094] When the radial reflector is axially moved to be opposite to the fuel region, the neutrons can be multiplied and reflected back to the fuel region, so as to increase the nuclear fission reaction rate in the core and increase the reactivity of the core. When the radial reflector is partially or entirely axially moved to be deviated from the position opposite to the fuel region, the neutron multiplication reaction process is reduced, the nuclear fission reaction rate in the core is reduced, and the reactivity of the core is reduced. When the radial reflector is axially moved out of the position opposite to the fuel region and the control ring is entirely located outside the position opposite to the fuel region, the core can be sub-critical, and the k eff <0.95, and the reactivity of the core is adjusted and controlled by combining the feedback of the reactivity instrument and moving the radial reflector in different axial directions.

[0095] Table 1: The core parameters of the Kilopower heat pipe reactor with 10kW electric power

[0096]

[0097]

[0098] Table 2: The relevant design parameters of the space reactor control system based on the double protection of the control ring and the reflector carried out on the Kilopower core with 10kW electric power

[0099]

[0100] As Figure 5 shown, the control scheme of the space reactor control system based on the double protection of the control ring and the reflector carried out on the Kilopower heat pipe reactor with 10kW electric power in the specific embodiment of the present application shows the influence of the axial height of the control ring in the case of the radial reflector being axially opposite to the core and the sand drop accident on the k eff of the core. Figure 6In a specific embodiment of the present invention, a control scheme based on a dual protection mechanism of a control loop and a reflector layer for a space reactor system was developed on a 10kW electric power heat pipe reactor, Kilopower. The control scheme involved the radial reflector layer being completely extracted axially towards the reactor core. Under a sand fall accident, the axial height of the control loop was adjusted relative to the reactor core k. eff The impact.

[0101] The results show that when the radial reflector is fully aligned with the core, in the event of a reactor fall-in-sand accident, the axial height of the B4C control ring above the core fuel zone is greater than 21 cm, which can achieve k eff The critical safety requirement of <0.98 is met; when the radial reflector is completely extracted axially and positioned directly opposite the core, the critical safety requirement can be met under various working conditions with different wet sand.

[0102] like Figure 7 As shown in the figure, in a specific embodiment of the present invention, a control scheme for a space reactor control system based on dual protection of control loop and reflector layer was carried out on a 10kW electric power heat pipe reactor Kilopower. The radial reflector layer is axially aligned with the reactor core. The axial height of the control loop is different relative to the reactor core k under different conditions during a launch accident and a water ingress accident. eff The impact; such as Figure 8 As shown, in a specific embodiment of the present invention, a control scheme based on a dual protection mechanism of a control loop and a reflector layer for a space reactor control system developed on a 10kW electric power heat pipe reactor Kilopower is presented. The control scheme is shown at the position where the radial reflector layer is completely extracted axially, directly opposite the reactor core. The axial height of the control loop is shown in relation to the reactor core k under different conditions during a launch accident or water ingress accident. eff The impact.

[0103] The results show that, with the radial reflector layer axially aligned with the core, and under conditions of reactor flooding, the axial height of the B4C control ring above the core fuel zone is greater than 19 cm, achieving k... eff The critical safety requirement is <0.98; under the extreme condition of complete reactor flooding, with the radial reflector fully extracted axially and directly opposite the core, k eff It will not exceed 0.895, which meets the critical safety requirements. For example... Figure 9 The image shows the transient effects of the normalized neutron density in the core under different positive reactivity values ​​introduced into the core of a space reactor control system based on dual protection of the control loop and reflector layer, implemented in a specific embodiment of the present invention on a 10kW electric power heat pipe reactor, Kilopower. Figure 10The figure shows the transient effect of the normalized neutron density in the core with time under the condition of introducing different negative reactivity values into the core of the Kilopower reactor with 10kW electric power heat pipe reactor, which is the control scheme of the space reactor control system based on the double protection of control ring and reflector layer in the specific embodiment of the application. Table 3 is the neutron dynamic transient parameter calculated by the space reactor control system based on the double protection of control ring and reflector layer for the Kilopower core scheme with 10kW electric power.

[0104] From Figure 9 , Figure 10 and Table 3, for the space reactor, since the fast reactor operation mode is usually adopted, the neutron generation time in the core is very short, and in the control scheme design, the safety thereof needs to be ensured, in the present scheme, due to the axial movement of the radial reflector and the control ring, two sets of protection mechanisms, have double safety effectiveness, and in the emergency shutdown system, a part of the electric energy converted by the thermoelectric conversion device or the charging of the energy storage battery as a backup power source can drive the mechanical driving devices of the control ring and the radial reflector, so that the effective control of the above two sets of double protection mechanisms is realized; if the above two power sources are lost, the radial reflectors in the four quadrants can be popped out to face the core position through the expansion effect of temperature and pressure, the neutron leakage rate of the core is increased, and it is ensured that the supercritical event of k eff >1 does not occur in the core, and the effective safety control of the space reactor is fully realized.

[0105] Table 3 Neutron dynamic transient parameters of the space reactor control system based on the double protection of control ring and reflector layer carried out on the Kilopower core with 10kW electric power

[0106]

[0107] From the above, the space reactor control system based on the double protection of control ring and reflector layer is constructed by the first step, the effective safety control of the space reactor is completed by the cooperation of the core fuel area, the control ring, the radial reflector, the axial reflector, the sensor and the energy storage component, the reactivity instrument and the emergency shutdown system in the second step, wherein the safety shutdown of the reactor can be realized by the two sets of adjustment schemes of the control ring and the radial reflector, and the double protection mechanism is provided; in the emergency shutdown system, a part of the electric energy converted by the thermoelectric conversion device or the charging of the energy storage battery as a backup power source can drive the mechanical driving devices of the control ring and the radial reflector, so that the effective control of the above two sets of double protection mechanisms is realized, and meanwhile, if the above two power sources are lost, the radial reflectors in the four quadrants can be popped out to face the core position through the expansion effect of temperature and pressure, the neutron leakage rate of the core is increased, and it is ensured that the supercritical event of k effThe supercritical event of 1, fully realizes the effective safety control of the space reactor.

[0108] The application can provide a safe and effective control scheme for future space reactor applications, can fully protect the safety of the reactor system and the environment, and can realize the miniaturization and light weight of the space reactor, and improve the durability and economic practicability of the system.

[0109] The above is only the preferred embodiment of the application, the protection scope of the application is not limited to the above-mentioned examples, any technical scheme belonging to the idea of the application is within the protection scope of the application. It should be pointed out that, for ordinary skilled in the art, some improvements and decorations without departing from the principle of the application should be considered as the protection scope of the application.

Claims

1. A space reactor control method based on dual protection of control loop and reflector layer, characterized in that, The method includes: A space reactor is constructed; the space reactor includes: a core fuel zone, an axial reflector layer, a radial reflector layer, a control ring, sensors, and a reactivity meter; the control ring is arranged between the core fuel zone and the radial reflector layer; the radial reflector layer is arranged radially outside the control ring; the reactivity meter is arranged around the radial reflector layer for real-time measurement of the reactivity of the space reactor core; sensors are arranged inside and outside the radial and axial reflector layers for measuring temperature and pressure; wherein, the reactivity of the core is negatively correlated with the area of ​​the control ring facing the core fuel zone and positively correlated with the area of ​​the radial reflector layer facing the core fuel zone; The control values ​​of the control loop and the radial reflection layer are designed separately, such that the control value of the radial reflection layer is greater than the control value of the control loop; the control value represents the reactive change value corresponding to a unit axial height movement; the ratio of the control value of the radial reflection layer to the control value of the control loop is (2~5):1; Obtain the currently measured reactivity, calculate the effective growth factor corresponding to the reactivity value, and when the temperature measured by the sensor does not exceed the preset temperature and the pressure does not exceed the preset pressure, calculate the absolute value of the difference between the preset effective growth factor of the core after adjustment and the current effective growth factor of the core. If the absolute value is greater than the preset value, the axial height of the radial reflective layer is adjusted according to the control value of the radial reflective layer; if the absolute value is not greater than the preset value, the axial height of the control ring is adjusted according to the control value of the control ring.

2. The method according to claim 1, characterized in that, The control value of designing the control loop and radial reflection layer separately includes: The control value of the control loop is specifically determined by adjusting the proportion of neutron absorbers in the control loop or the inner and outer radial dimensions of the control loop. The higher the proportion of neutron absorbers, the greater the control value of the control loop. The larger the geometric volume corresponding to the inner and outer radial dimensions, the greater the control value of the control loop. The control value of designing a radial reflector layer specifically includes: adjusting the proportion of neutron multiplier material in the radial reflector layer, or the inner and outer radial dimensions of the radial reflector layer; among them, the higher the proportion of neutron multiplier material, the greater the control value of the radial reflector layer; the larger the geometric volume corresponding to the inner and outer radial dimensions, the greater the control value of the radial reflector layer.

3. The method according to claim 1, characterized in that, The radial reflective layer is divided into four sections according to the four quadrants; If the absolute value is greater than the preset value, the axial height of the radial reflective layer is adjusted according to the control value of the radial reflective layer, including: The range of values ​​greater than the preset value is divided into four preset ranges; When the absolute value is within the first interval, the axial height of the corresponding radial reflective layer is adjusted sequentially from the first quadrant to the fourth quadrant until the absolute value is not greater than the preset value. When the absolute value is within the second interval, first adjust the axial height of the radial reflective layer in the first and third quadrants until the absolute value is not greater than the preset value or reaches the adjustment limit. If the absolute value is still greater than the preset value when the adjustment limit is reached, then adjust the axial height of the radial reflective layer in the second and fourth quadrants in turn until the absolute value is not greater than the preset value. When the absolute value is within the third interval, first adjust the axial height of the radial reflective layer in the first quadrant, the second quadrant, and the third quadrant until the absolute value is not greater than the preset value or reaches the adjustment limit. If the absolute value is still greater than the preset value when the adjustment limit is reached, then adjust the axial height of the radial reflective layer in the fourth quadrant until the absolute value is not greater than the preset value. When the absolute value is within the fourth interval, the axial height of the radial reflective layer corresponding to the four quadrants is adjusted simultaneously until the absolute value is not greater than the preset value. The degree of closeness between the four preset intervals and the preset values ​​decreases sequentially from the first interval to the fourth interval.

4. The method according to claim 3, characterized in that, The method further includes: If the preset effective multiplication factor of the core after adjustment cannot be achieved even if all four radial reflector layers exceed the distance of axial movement, then the axial movement of the drive control loop will be performed.

5. The method according to claim 1, characterized in that, The corresponding effective proliferation factor is calculated based on the reactivity value, including: Where, k eff ρ represents the effective multiplication factor, and ρ represents the reactivity of the space reactor core.

6. The method according to claim 1, characterized in that, There are vacuum gaps between the control ring and the core fuel zone and the radial reflector layer.

7. The method according to claim 1, characterized in that, The reactor core fuel region includes the start-up neutron source, fuel elements, heat-conducting elements, and matrix materials; The hot end of the heat-conducting element is arranged around the fuel element, and the cold end is connected to the thermoelectric conversion device to carry out the heat released by the fuel element and convert it into electrical energy through the thermoelectric conversion device. The heat-conducting element is a liquid alkali metal heat pipe or a cooling circuit pipe containing a cooling medium; the cooling medium is an inert gas or a liquid metal. The thermoelectric conversion device is a thermoelectric generator or a Stirling engine.

8. The method according to claim 7, characterized in that, The method further includes: When the temperature measured by the sensor exceeds the preset temperature, the pressure exceeds the preset pressure, and a portion of the electrical energy converted by the thermoelectric conversion device can drive the axial height adjustment device, the axial height of the radial reflector is adjusted so that the radial reflector is partially or completely offset from the core fuel area, or the axial height of the control ring is adjusted so that the control ring is partially or completely aligned with the core fuel area, in order to reduce reactivity.

9. The method according to claim 1, characterized in that, The sensor consists of a strain gauge and a data acquisition box; The space reactor also includes: an emergency shutdown system and energy storage components; The emergency shutdown system includes a power supply unit; The energy storage component includes a thermocouple and an energy storage battery connected together. The thermocouple can convert thermal energy into electrical energy and charge the energy storage battery, enabling the energy storage battery to serve as a backup power source.

10. The method according to claim 9, characterized in that, The method further includes: When the temperature measured by the sensor exceeds the preset temperature, the pressure exceeds the preset pressure, and the electrical energy converted by the thermoelectric conversion device is insufficient to drive the axial height adjustment device of the control ring and the radial reflective layer, the energy storage battery is activated to provide power to adjust the axial height of the control ring or the radial reflective layer in order to reduce reactivity. When the temperature measured by the sensor exceeds the preset temperature, the pressure exceeds the preset pressure, and the electrical energy converted by the thermoelectric conversion device is insufficient to drive the axial height adjustment device, and the energy storage battery loses power, the radial reflector layer will be ejected to ensure that the core does not experience a supercritical event.

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